Study On The Treatment Of Sapogenin Wastewater By Two-phase Anaerobic Digestion With Three Stages

Sapogenin industry is an important biological, medical and chemicalindustry. Sapogenin wastewater is difficult to treat for its high concentrationof acid and organic matters, and it will bring serious pollution if it isn't treatedproperly. Sapogenin's main producing areas are in upriver area of Hanjiang.Therefore Sapogenin wastewater engenders a threat to the water source ofcentre line of South-North water Diversion.Considering the chemical character of Sapogenin wastewater, wedeveloped "the two-phase anaerobic digestion with three stages process" thatcontains an acidification phase, an inner electrolysis and a methane phase. Wehad laboratory trials and industry trials for this technology. Followings are ourtrial results.1. On the laboratory scale, comparative trials for treating Sapogeninwastewater were done by using three following technologies: the single phaseanaerobic digestion, the two-phase anaerobic digestion and the two-phaseanaerobic digestion with three stages. The experimental results demonstratedthat the COD removal, the sulfate removal and the methane yield of thetwo-phase anaerobic digestion with three stages is obviously better than thatof the single phase anaerobic digestion or that of the two-phase anaerobicdigestion.2. In this paper, we studied the functioning principles of the innerelectrolysis in "the two-phase anaerobic digestion with three stages".Comparative trials were taken to analyze the effects of the position of theinner electrolysis. Study showed that better effect could be achieved when theinner electrolysis was placed between the acidification phase and the methanephase. Experimental results showed that inner electrolysis decreased ORP, buffered pH, increased microelements, degraded toxicity and optimizedanaerobic circumstance.3. In the zero and first grade reaction the kinetic constant of three typesof anaerobic digestion was worked out through comparative trials on kineticanalysis.4. We adopted the technology that consists of "physical and chemicaltreatment+anaerobic digestion + aerobic digestion + oxidation decoloration"to treat Sapogenin wastewater in industry field. The whole equipment ofthis technology runned well and the total COD removal rate reached 99.4%.The treatment efficiency was maintained at total COD removal of over 99.4%.The effluent of this technology can fulfill the discharge standard of pollutantsfor sapogenin wastewater.